JPS6147273B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention fixes the cutting edge of drilling equipment for oil wells, geothermal extraction wells, etc. or tunnel drilling equipment, especially the tip of a drill pipe, inserts it into the ground, and rotates the drill pipe to make a hole. This invention relates to a drill bit used in a drilling rig that is lifted above the ground together with a drill pipe.

Conventionally, as shown in FIG. 1, two or three drill bits equipped with a rotary cutter protrude forward from the side surface of a base 1 formed so as to be connected to a drill pipe, and are integrated with the base 1 symmetrically along the center line. A bearing 3 is formed at the end of the branch part 2 so as to protrude obliquely forward toward the center line of the base part 1.
Cutters 4 having the same outer diameter are rotatably provided on the bearing 3 in close contact with each other, and these cutters 4 cut one continuous surface of the hole bottom.

In the present invention, since the bit is rotated around the center line of the drill pipe, the circumferential speed of the cutter at the center of the hole is smaller than the circumferential speed at the outer circumference. Focusing on the point that cutting speed is a constraint, if you excavate in an annular manner starting from the peripheral area where the circumferential speed is high, the central part that remains in the shape of a core can be easily crushed because it protrudes toward the center, and the excavation speed can be reduced. This focuses on things that can be improved.

The present invention embodies this technical idea in a bit having a rotating cutter.

The basic structure of the bit of the present invention will be explained with reference to FIG. 2. A cylindrical base 1 with a hollow interior 8 and an open end is provided with a screw 1' on the outer periphery of one end.
It can be connected to the lower end of the drill pipe by means of a screw 1', allowing high-pressure water sent through the drill pipe to communicate with the interior 8. The other end surface 7 of the base 1 is closed, and a plurality of central nozzle holes 9 are provided in the closed other end surface 7 so as to communicate from the inside of the base 1 to the outside. A branch-shaped portion 2 is integrally provided from the side surface of the base 1 and extends forward from the other end surface 7 of the base 1. Although only one branch 2 is shown in the figure, two or three branches of the same size are provided around the center line A of the base 1 at equal intervals. A bearing 3 is formed at the tip of each branch 2 to protrude diagonally forward toward the centerline A of the base 1, and the intersection of the centerline B of the bearing 3 and the centerline A of the base 1 is the same. It is set up so that A central nozzle hole 9 is connected to the bearing 3 via a roller bearing 5 and a ball bearing 6.
An outer cutter 4 having the same external shape is rotatably attached to excavate the outer circumference of the excavation area. When this cutter is rotated from the ground through a drill pipe and high-pressure water is ejected from the center nozzle hole 9 of the cutter through the drill pipe to drill underground, the cross section of the drilled hole bottom 10 will be as shown in FIG. become. That is, the outer periphery of the hole bottom 10 is cut in advance in an annular manner by the outer periphery cutter 4 . A cylindrical core 12 is formed at the center of the annular groove 11 created by this cutting. Since the sides of the core 12 are open, it can be easily crushed by high-pressure water jetted from the top surface 13 of the core 12 from the central nozzle hole 9. Therefore, the drilling speed can be greatly improved by using the bit of the present invention compared to drilling using the conventional bit shown in FIG.

The basic form of the bit of the present invention, which has a set of a plurality of identical branch parts having the same cutter, has been explained above, but in the case of a bit with a large borehole diameter,
The distance from the other end surface 7 of the base 1 to the intersection of the center line B of the bearing 3 and the center line A of the base 1 and the cutting inner diameter of three sets of branch-shaped parts are sequentially increased. If the bits are arranged in order from the smallest set to the largest set with the smallest distance and inner diameter as they move away from the bit, the cross section of the bottom of the drilled hole formed by this bit will have a step-like protrusion in the center as shown in FIG.
In FIG. 4, 11 is the part of the annular groove cut by the set of branch parts having the largest distance and the inner diameter of the excavation, and 14 is the part of the annular groove cut by the set of branch parts having the smallest distance and inner diameter. Stepped cutting part, 15 is 1
The stepped cut is made by a set of branches of said distance and inner diameter intermediate between 4 and 11.

By providing a plurality of sets of branch portions in this manner, large-diameter holes can be easily cut, and the excavation speed can be increased more than conventionally.

In the bit of the present invention, each of the branch parts of the set of branch parts is arranged symmetrically with respect to the center line of the base in order to provide balance with respect to the center of rotation. If the center of gravity is eccentric, it will cause rotational wobbling and press against the hole wall, acting as a brake against the rotational force applied from the ground, not only causing wear on the bit and drill pipe, but also shortening the life of the cutter.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional underground drilling drill bit equipped with a rotary cutter, and FIG. 2 is a partial vertical sectional view of the basic form of an underground drilling drill bit according to the present invention.
3 is a sectional view of the bottom of a hole drilled by the bit shown in FIG. 2, and FIG. 4 is a sectional view of the bottom of a hole drilled by still another embodiment of the bit of the present invention. 1... Base, 2... Branch, 3... Bearing, 4...
...Outer cutter, 5...Roller bearing, 6
... Ball bearing, 7 ... Other end surface, 8 ... Inside, 9 ... Central nozzle hole, 10 ... Hole bottom, 11 ...
... annular groove, 12 ... core, 13 ... top surface, 14,
15...Stepped cutting part.

Claims (1)

[Claims] 1. A hollow base formed to be attachable so that one end can communicate with a drill pipe, and a central nozzle hole formed in the other closed end surface of the base so as to communicate from the inside of the base to the outside. a plurality of branch parts extending from the side of the base to the front from the other end face of the base and formed integrally with the base; and a bearing formed at the tip of the branch part to protrude diagonally forward toward the center line of the base. , an outer circumferential cutter rotatably provided on the bearing so as to excavate the outer periphery of the excavation area by the central nozzle hole, and the branch portion is provided so that the intersection of the center line of the bearing and the center line of the base portion is the same. An underground drilling drill bit comprising at least one set of a plurality of cutters having the same outer diameter and arranged at equal intervals around the center line of the base. 2. A plurality of sets of branch portions each having a distance from the other end surface of the base to the intersection of the center line of the bearing and the center line of the base and a cutting inner diameter that are sequentially increased, and each set of branch portions is connected to the other end surface of the base. 2. The underground drilling drill bit according to claim 1, wherein both the distance and the inner diameter are arranged sequentially from the smallest set to the largest set as the distance from the ground increases.